Doping of inorganic materials in microreactors – preparation of Zn doped Fe₃O₄ nanoparticles

Microreactor systems are now used more and more for the continuous production of metal nanoparticles and metal oxide nanoparticles owing to the controllability of the particle size, an important property in many applications. Here, for the first time, we used microreactors to prepare metal oxide nanoparticles with controlled and varying metal stoichiometry. We prepared and characterised Zn-substituted Fe₃O₄ nanoparticles with linear increase of Zn content (ZnxFe₃−xO₄ with 0 ≤ x ≤ 0.48), which causes linear increases in properties such as the saturation magnetization, relative to pure Fe₃O₄. The methodology is simple and low cost and has great potential to be adapted to the targeted doping of a vast array of other inorganic materials, allowing greater control on the chemical stoichiometry for nanoparticles prepared in microreactors

A flexible one-pot route to metal/metal oxide nanocomposites

We report a one-pot route to Au/CeO2 nanocomposites. A readily-available biopolymer, sodium alginate, is exploited for controlled formation and stabilisation of gold nanoparticles followed by in situ growth of a sponge-like network of CeO2 nanoparticles. The flexible nature of this method as a general route to mixed metal/metal oxide nanocomposites is also demonstrated

Room-temperature ferromagnetism in nanoparticles of superconducting materials

Nanoparticles of superconducting YBa2Cu3O7-delta (YBCO) (Tc = 91 K) exhibit ferromagnetism at room temperature while the bulk YBCO, obtained by heating the nanoparticles at high temperature (940 degree C), shows a linear magnetization curve. Across the superconducting transition temperature, the magnetization curve changes from that of a soft ferromagnet to a superconductor. Furthermore, our experiments reveal that not only nanoparticles of metal oxides but also metal nitrides such as NbN (Tc = 6 - 12 K) and delta-MoN (Tc ~ 6 K) exhibit room-temperature ferromagnetism.Comment: 11 pages, 6 figure

Mixed metal nanoparticle assembly and the effect on surface enhanced raman scattering

Here we report the assembly of mixed metal nanoparticles using an oligonucleotide-templated approach. Substitution of one of the gold nanoparticle probes with an analagous silver probe to produce a hetero-metal duplex permitted surface enhanced Raman scattering of the dye label, exploiting the improved surface enhancement properties of silver nanoparticles whilst maintaining the surface chemistry benefits of gold nanoaprticle

Dry impregnation in fluidized bed: Drying and calcination effect on nanoparticles dispersion and location in a porous support

The synthesis of metal nanoparticles dispersed inside the grains of a porous inorganic support was carried out by ‘‘dry impregnation’’ in a fluidized bed. The principle of this technique consists in the spraying of a solution containing a metal source into a hot fluidized bed of porous particles. The metal source can be of different nature such as metal salts, organometallic precursors or colloidal solutions. The experimental results obtained from iron oxide deposition on a porous silica gel as support, constitute the core of this article but others results concerning the deposition of rhodium from a colloidal suspension containing preformed rhodium nanoparticles are also described. More precisely, this study aims to understand the effect of the bed temperature during the impregnation step, the initial particle porosity and the calcination operating protocol on the metallic nanoparticles dispersion and location in the silica porous particles. The so-obtained products were characterized by various techniques in order to determine their morphology, their surface properties and the dispersion of the nanoparticles inside the support. The results showed that, under the chosen operating conditions, the deposit efficiency is close to 100% and the competition between the drying rate, depending on the process-related variables, and the capillary penetration rate, depending on the physicochemical-related variables, controls the deposit location. A quasi uniform deposit inside the support particles is observed for soft drying. The metal nanoparticles size is controlled by the pore mean diameter of the support as well as the calcination operating protocol

Hydrophobic and hydrophilic au and ag nanoparticles. Breakthroughs and perspectives

This review provides a broad look on the recent investigations on the synthesis, characterization and physico-chemical properties of noble metal nanoparticles, mainly gold and silver nanoparticles, stabilized with ligands of different chemical nature. A comprehensive review of the available literature in this field may be far too large and only some selected representative examples will be reported here, together with some recent achievements from our group, that will be discussed in more detail. Many efforts in finding synthetic routes have been performed so far to achieve metal nanoparticles with well-defined size, morphology and stability in different environments, to match the large variety of applications that can be foreseen for these materials. In particular, the synthesis and stabilization of gold and silver nanoparticles together with their properties in different emerging fields of nanomedicine, optics and sensors are reviewed and briefly commented

Synthesis of Supported Catalysts by Dry Impregnation in Fluidized Bed

The synthesis of catalytic or not composite materials by dry impregnation in fluidized bed is described. This process can be carried out under mild conditions from solutions of organometallic precursors or colloidal solutions of preformed nanoparticles giving rise to reproducible metallic nanoparticles containing composite materials with a high reproducibility. The adequate choice of the reaction conditions makes possible to deposit uniformly the metal precursor within the porous matrix or on the support surface. When the ratio between the drying time and the capillary penetration time (tsec/tcap) is higher than 10, the impregnation under soft drying conditions leads to a homogeneous deposit inside the pores of the particles of support. The efficiency of the metal deposition is close to 100%, and the size of the formed metal nanoparticles is controlled by the pores diameter. Finally, some of the presented composite materials have been tested as catalysts: iron-based materials were used in carbon-nanotubes synthesis, while Pd and Rh composite materials have been investigated in hydrogenation reactions